Modular columnar electroluminescent display control circuit

Abstract

The electroluminescent display provides a columnar, bar, or the like incremental analog presentation of an unknown unidirectional electric signal amplitude. Employing a stacked array of luminescent diodes, each diode of the diode array is associated with a circuit element controlled by a voltage comparator and an illumination intensity modulation source. The control circuits and diodes are adapted to use in simple cascaded modular circuit form permitting a wide range of choices of the number of diodes in the bar display and therefore, of its useful voltage indicating range. Variable pulse duty cycle brightness control is afforded.

I claim: 
     
       1. A bar graph display comprising: a plural number of electroluminescent semiconductor diode means disposed in a contiguous manner in lineal array,   first reference voltage source means for providing a first voltage,   second reference voltage source means for providing a second voltage,   tapped voltage divider means coupled between said first and said second voltage source means, said tapped voltage divider means having a number of tap means equal to said plural number, and including series connected first resistors having equal resistances,     a number of voltage comparator means equal to said plural number, each successive voltage comparator means being coupled to a corresponding successive one of said tap means,   each said successive voltage comparator means being additionally responsive to an input signal of unknown magnitude for forming a first or a second discrete comparison output,     second resistors of second equal resistances for coupling in parallel said input signal of unknown magnitude to each said respective successive voltage comparator means,   bias voltage source means,   each said successive electroluminescent semiconductor diode means being responsive separately to said bias voltage source means and to a corresponding one of said discrete comparison outputs,   third resistors of third equal resistances for coupling in parallel said bias voltage source means to each successive electroluminescent diode means,   a number of NAND gate means equal to said plural number, each said NAND gate means having first and second input means and one output means,   said first input means being responsive to a corresponding one of said discrete comparison outputs, and   said one output means being coupled to said bias voltage source means,     means for coupling adjustable width pulse generator means to said second input means of said NAND gate means for selectively adjusting the illumination level of said electroluminescent semiconductor diode array with respect to the ambient illumination condition, and   signal generator means coupled to said pulse generator means for excitation of said pulse generator means at a repetition frequency chosen so that flicker is absent from said electroluminescent semiconductor diode array.